This application claims benefit of priority under 35 U.S.C. xc2xa7 119 to Japanese Patent Application No. 2000-35824, filed on Feb. 14, 2000, the entire contents of which are incorporated by reference herein.
1. Field of the Invention
The present invention relates to a radio communication system in which a terminal communicates by radio through a repeater, and more particularly to a radio communication system allowing continuous communication under an environment where shielding objects move by selecting a terminal in an optimum receiving condition, a radio communication method and a recording medium for storing a program for selection of a repeater in the radio communication system.
2. Description of the Related Art
In a conventional radio communication for communicating with a moving terminal through a public communication network, if field intensity of electronic wave received by the moving terminal weakens, the moving terminal switches its base station so as to continue the communication.
Here, a radio communication system using the conventional public communication network will be described with reference to FIG. 1. In the radio communication system shown in FIG. 1, field intensity of electronic wave received by a moving terminal 51 is detected.
If the field intensity of the received electronic wave weakens as this moving terminal 51 moves, the moving terminal 51 dispatches a communication channel switching request to a base station 52 on communication. This switching request is sent from the base station 52 to a control station 53 and then, this control station 53 notifies the moving terminal 51 of a base station 54 which has the highest receiving level of plural base stations from which the moving terminal 51 can receive electronic wave as a new base station. Consequently, the moving terminal 51 can switch communication to the base station 54 located in an area to which the moving terminal 51 moves, so that it can continue communication during moving.
In this radio communication system, when switching the base station, a communication channel between the moving terminal 51 and the base station 52 on communication is kept and if a new communication channel capable of communicating at a receiving level from the base station 54 located in an area to which the moving terminal 51 moves is found, communication with the base station 54 is started through the new communication channel.
This conventional radio communication system produces no problems under a communication system which assumes that field intensity drops gradually when the moving terminal 51 moves as seen in a wide area based on the public communication network and allows communication through a currently used communication channel in a while during the moving. However, the conventional radio communication system cannot be applied to such an environment in which the field intensity drops suddenly when the terminal or shielding object moves like in communication in a small area.
Particularly, the field intensity is proportional to 1/(distance)2 and thus depends upon a distance between the moving terminal and base station. In case where the unit of distance is large like in communication system using the public communication network, even if the distance changes more or less, the field intensity never changes largely. However, if the unit of distance is small like in indoor radio communication system in vehicle compartment or factory, the field intensity changes largely due to a slight change of the distance.
Further, the indoor radio communication system employs a minute or small output power. Thus, if such a shielding object as wall, man, chair or equipment moves near communication path, electronic wave damps largely even if the distance is not changed, so that communication maybe sometimes disabled.
In indoor radio LAN system shown in FIG. 2, repeaters 62a, 62b, 62c connected to the wired LAN 61 are provided on ceiling and terminals 63a, 63b, 63c are communicating with a repeater located just vertically above. That is, the terminal 63a is communicating with the repeater 62a, the terminal 63b is communicating with the repeater 62b and the terminal 63c is communicating with the repeater 62c. Consequently, this radio communication system lowers a possibility that communication between the terminal and repeater is interrupted.
This radio LAN system can secure a sufficient space just vertically above the terminal and any shielding object never enters between the repeater and the terminal. Further, the above described problem can be solved under an environment in which the terminal and shielding object are semi-fixed, like office. However, there is a possibility that any shielding object may enter between the terminal and the repeater under such an environment in which no sufficient space can be secured as the vehicle compartment and factory, so that the above-described problem cannot be solved.
The present invention has been achieved in views of the above described problem and therefore an object of the present invention is to provide a radio communication system capable of securing continuous communication even under an environment in which no sufficient space can be secured and a terminal or shielding object moves, by selecting a repeater which secures an optimum communication state from plural repeaters, a radio communication method thereof and a recording medium for storing a program for selection of a repeater in radio communication system.
To achieve the above described object, according to an aspect of the invention, there is provided a radio communication system for a terminal to carry out radio communication through a repeater securing an optimum communication state selected from plural repeaters, wherein a reception condition of a repeater when each of plural repeaters receives a connection request sent from the terminal through broadcast is detected as a repeater reception condition and a reception condition of a terminal when the terminal receives a connection request echo sent from the plural repeaters after receiving the connection request is detected as a terminal reception condition so as to select a repeater securing an optimum communication state based on the terminal reception condition and the repeater reception condition.
According to the present invention, communication is carried out always by selecting a repeater securing an optimum communication with each terminal. Therefore, this communication method enables continuous communication to be carried out under such an environment in which no sufficient space can be secured and a terminal and a shielding object move, as vehicle compartment and factory.
Further, to achieve the above object, according to another aspect of the invention, there is provided a radio communication system for a terminal to carry out radio communication through a repeater securing an optimum communication state selected by a path management repeater from plural repeaters, the system comprising: a terminal for sending a connection request for starting radio communication through broadcast, receiving a connection request echo sent back by a repeater receiving the connection request so as to detect a reception condition at this time as a terminal reception condition and sending the terminal reception condition through broadcast; plural repeaters for receiving the connection request sent by the terminal so as to detect a reception condition at this time as a repeater reception condition, sending the connection request echo including the repeater reception condition to the terminal and the path management repeater and when receiving the terminal reception condition sent by the terminal, sending the terminal reception condition to the path management repeater; and a path management repeater for receiving the connection request sent by the terminal so as to detect a reception condition at this time as a repeater reception condition, sending the connection request echo including the repeater reception condition to the terminal and when receiving the connection request echo sent by the plural repeaters and the terminal reception condition sent by the terminal or the plural repeaters, selecting a repeater securing an optimum communication state based on the repeater reception condition and the terminal reception condition.
According to the present invention, communication is carried out always by selecting a repeater securing an optimum communication with each terminal. Therefore, this communication method enables continuous communication to be carried out under such an environment in which no sufficient space can be secured and a terminal and a shielding object move, as vehicle compartment and factory.
According to still another aspect of the invention, there is provided a radio communication system for a terminal to carry out radio communication through a repeater securing an optimum communication state selected from plural repeaters, the system comprising: a terminal for sending a connection request for starting radio communication through broadcast, receiving a connection request echo sent back by a repeater receiving the connection request so as to detect a reception condition at this time as a terminal reception condition and selecting a repeater securing an optimum communication state based on the terminal reception condition and a repeater reception condition included in the connection request echo; and plural repeaters for receiving the connection request sent by the terminal so as to detect a reception condition at this time as the repeater reception condition and sending the connection request echo including the repeater reception condition to said terminal.
According to the present invention, communication is carried out always by selecting a repeater securing an optimum communication with each terminal. Therefore, this communication method enables continuous communication to be carried out under such an environment in which no sufficient space can be secured and a terminal and a shielding object move, as vehicle compartment and factory.
Further, to achieve the above described object, according to a further aspect of the invention, there is provided a radio communication method for a terminal to carry out radio communication through a repeater securing an optimum communication state selected by a path management repeater from plural repeaters, the method comprising: a connection request sending step of said terminal""s sending a connection request for starting radio communication through broadcast; a repeater reception condition detecting step of when the connection request sent in the connection request sending step is received by the plural repeaters and the path management repeater, detecting a reception condition at this time as a repeater reception condition; a connection request echo sending step of sending a connection request echo including the repeater reception condition detected in the repeater reception condition detecting step to the terminal and the path management repeater; a terminal reception condition detecting step of when the terminal receives the connection request echo sent in the connection request echo sending step, detecting a reception condition at this time as a terminal reception condition; a terminal reception condition sending step of sending the terminal reception condition detected in the terminal reception condition detecting step through broadcast; a terminal reception condition echo sending step of when the plural repeaters receive the terminal reception condition sent in the terminal reception condition sending step, sending back the terminal reception condition to the path management repeater; and a repeater selection step of when the path management repeater receives the terminal reception condition sent in the terminal reception condition echo sending step or the terminal reception condition sending step and further receives the connection request echo sent back in the connection request echo sending step, selecting a repeater securing an optimum communication state based on the terminal reception condition and the repeater reception condition.
According to the present invention, communication is carried out always by selecting a repeater securing an optimum communication with each terminal. Therefore, this communication method enables continuous communication to be carried out under such an environment in which no sufficient space can be secured and a terminal and a shielding object move, as vehicle compartment and factory.
Further, to achieve the above described object, according to a still further aspect of the invention, there is provided a radio communication method for a terminal to carry out radio communication through a repeater securing an optimum communication state selected from plural repeaters, the method comprising: a connection request sending step of the terminal""s sending a connection request for starting radio communication through broadcast; a repeater reception condition detecting step of when the connection request sent in the connection request sending step is received by the plural repeaters, detecting a reception condition at this time as a repeater reception condition; a connection request echo sending step of sending a connection request echo including the repeater reception condition detected in the repeater reception condition detecting step to the terminal; a terminal reception condition detecting step of when the terminal receives the connection request echo sent in the connection request echo sending step, detecting a reception condition at this time as a terminal reception condition; and a repeater selection step of selecting a repeater securing an optimum communication state based on the terminal reception condition detected in the terminal reception condition detecting step and the repeater reception condition included in the connection request echo.
According to the present invention, communication is carried out always by selecting a repeater securing an optimum communication with each terminal. Therefore, this communication method enables continuous communication to be carried out under such an environment in which no sufficient space can be secured and a terminal and a shielding object move, as vehicle compartment and factory.
To achieve the above described object, according to a yet still further aspect of the present invention, there is provided a recording medium for storing a program for selection of a repeater in radio communication system for a terminal to carry out radio communication through a repeater securing an optimum communication state selected by a path management repeater from plural repeaters, the program including: a connection sending request processing for the terminal""s sending a connection request for starting radio communication through broadcast; a repeater reception condition detecting processing for, when the connection request sent in the connection request sending processing is received by the plural repeaters and the path management repeater, detecting a reception condition at this time as a repeater reception condition; a connection request echo sending processing for sending a connection request echo including the repeater reception condition detected in the repeater reception condition detecting processing to the terminal and the path management repeater; a terminal reception condition detecting processing for, when the terminal receives the connection request echo sent in the connection request echo sending processing, detecting a reception condition at this time as a terminal reception condition; a terminal reception condition sending processing for sending the terminal reception condition detected in the terminal reception condition detecting processing through broadcast; a terminal reception condition echo sending processing for, when the plural repeaters receive the terminal reception condition sent in the terminal reception condition sending processing, sending back the terminal reception condition to the path management repeater; and a repeater selection processing for, when the path management repeater receives the terminal reception condition sent in the terminal reception condition echo sending processing or the terminal reception condition sending processing and further receives the connection request echo sent back in the connection request echo sending processing, selecting a repeater securing an optimum communication state based on the terminal reception condition and the repeater reception condition.
According to the present invention, communication is carried out always by selecting a repeater securing an optimum communication with each terminal. Therefore, this communication method enables continuous communication to be carried out under such an environment in which no sufficient space can be secured and a terminal and a shielding object move, as vehicle compartment and factory.
To achieve the above described object, according to a yet still further aspect of the present invention, there is provided a recording medium for storing a program for selection of a repeater in radio communication system for a terminal to carry out radio communication through a repeater securing an optimum communication state selected from plural repeaters, the program including: a connection request sending processing for the terminal""s sending a connection request for starting radio communication through broadcast; a repeater reception condition detecting processing for, when the connection request sent in the connection request sending processing is received by the plural repeaters, detecting a reception condition at this time as a repeater reception condition; a connection request echo sending processing for sending a connection request echo including the repeater reception condition detected in the repeater reception condition detecting processing to the terminal; a terminal reception condition detecting processing for, when the terminal receives the connection request echo sent in the connection request echo sending processing, detecting a reception condition at this time as a terminal reception condition; and a repeater selection processing for selecting a repeater securing an optimum communication state based on the terminal reception condition detected in the terminal reception condition detecting processing and the repeater reception condition included in said connection request echo.
According to the present invention, communication is carried out always by selecting a repeater securing an optimum communication with each terminal. Therefore, this communication method enables continuous communication to be carried out under such an environment in which no sufficient space can be secured and a terminal and a shielding object move, as vehicle compartment and factory.
The nature, principle and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.